** Oil producer's shares down 3.6 pct, secondlargest FTSE midcap loser, after UBS cuts rating on coto "sell", PT to 75p from 130p
** UBS analysts cut 2015-2019 oil price forecast to$80/barrel from $90/barrel, hurting expected earnings for oilproducers
** UBS calls Premier's Sea Lion project "unsanctioned,logistically challenging, high cost"; adds that co is highlygeared
** Co had a net-debt/EBITDA ratio of 5.28 at June 30 2015,according to Thomson Reuters data, compared with sector medianof 2.75
** Nomura cuts PT to 90p from 140p, also citing risk in SeaLion project and high oil price sensitivity
** UBS upgrades BP to "buy", Nomura upgrades BG to "buy", both stocks trading roughly in line with FTSE100 (venkateshasoumithri.mamidipudi.thomsonreuters.com@reuters.net)